Nitric oxide and peroxynitrite are reactive, short-lived species that are important mediators of various forms of hypoxia - reperfusion injury. One of the dow5nstream pathways of peroxynitrite-mediated organ injury is related to activation of the nuclear enzyme poly (ADP-ribose) synthetase (PARS). Based on in vitro and in vivo preliminary data, the applicants propose that the PARS pathway may play a role in the pathogenesis of the reperfusion injury associated with the transplantation of hypoxic organs, and propose studies to directly test the hypothesis that PARP inhibition supplementation in the organ storage fluid is able to improve the function of the transplanted organ. The first aim of the current project is to establish time course of PARS activation and associated organ dysfunction in an experimental kidney transplantation model, and to correlate these alterations with reactive nitrogen species formation in the organ. Reactive nitrogen species formation and PARS activation will be investigated using immunohistochemistry, and organ function will be investigated using conventional techniques. The second aim of the project is to perform direct studies into the role of PARS-related transplantation-induced kidney dysfunction. We will compare traditional organ preservation fluids with ones spiked with a novel potent PARS inhibitor, followed by evaluation of changes in the kidney function associated with transplantation. We will also evaluate the effect of treatment of the recipient with PARS inhibitor. Our studies will provide novel mechanistic information on ischemic storage and transplantation-related renal dysfunction which will be utilized for the future design and commercial development of novel organ preservation fluids.